1. Field of the Invention
This invention relates to heat-transfer recording and more particularly, to dye-receiving sheets for use in thermal transfer recording systems in which a dye transfer sheet is heated in an imagewise pattern by means of a heat source such as a thermal head or laser beam and a dye contained in the dye transfer sheet is sublimated or vaporized to record an intended image on a dye-receiving layer of the dye-receiving sheet.
2. Description of the Prior Art
Known dye-receiving sheets can be broadly classified into the following three groups with respect to the dyeing layer thereof.
(1) A dye-receiving layer made of a crosslinked product of a composition which comprises from 20 to 98 parts by weight of a thermoplastic resin having good dyeing affinity and, correspondingly, from 80 to 2 parts by weight of a compound having, in one molecule thereof, at least two radically polymerizable unsaturated bonds (Japanese Laid-open Patent Application No. 58-212994).
(2) A dye-receiving layer consisting of a thermoplastic polyester resin and a crosslinked polymer resin (Japanese Laid-open Patent Application No. 58-215398).
(3) Formation of a UV-cured resin film on polyvinyl chloride articles (Japanese Laid-open Patent Application No. 58-162374).
These dye-receiving sheets have the following drawbacks.
(a) Because the compound having radically polymerizable unsaturated bonds in (1) does not have good dyeing properties, the recording density lowers owing to the incorporation of the compound in the dye-receiving layer.
(b) The dye-receiving layer proposed in (2) does not have a satisfactory heat resistance. If the thermal transfer recording or printing is effected such that a dye transfer sheet and a dye image acceptor sheet are run at different speeds for recording, the resin carrying the dye on the dye transfer sheet thermally sticks with the dye acceptor sheet. For instance, when the dye transfer sheet is fed at a rate of 1/n, in which n&gt;1, relative to the the running speed of the image acceptor sheet, the thermal sticking takes place, so that the dye transfer sheet and the dye acceptor sheet cannot be run at predetermined speeds. The above running mode may be hereinafter referred to as "n-fold variable mode".
(c) The technique proposed in (3) is a so-called sublimation printing technique in which printing is effected using sublimable dyes. This technique does not ensure satisfactory dyeing affinity when high temperature recording is effected within a short time in the order of milliseconds.
(d) In (3), a UV-cured film is formed, but it is inevitable that a UV-curing resin or UV-curing initiator remain unreacted and thus, react with dyes. Accordingly, the accepted dye inconveniently undergoes discoloration and decoloration.